1. Field of the Invention
The present invention relates to a resinous composition for foul releasing coat and a coated article using the same.
2. Description of the Prior Art
As a coating material for forming an endurable coating film for the purpose of protecting the surface of a substrate such as an organic substrate such as wood substrate, plastic substrate and the like; an inorganic substrate such as a glass substrate, inorganic substrate for a construction material (for example, an inorganic cured body such as a concrete, slate, cement), metal substrate (for example, a steel plate such as stainless, non-ferrous metal such as aluminum) and the like, there are known a coating composition obtained by hydrolytic polycondensation or partial hydrolytic polycondensation of a hydrolyzable organosilane or a coating composition obtained by mixing a colloidal silica with the afore-said coating composition.
For example, Japanese Patent Kokai Publication 2736/1976, 2737/1976, 130732/1978 and 168470/1988 propose a coating material comprising an organo alkoxysilane, a hydrolytic polycondensate and/or partial hydrolytic polycondensate of the organo alkoxysilane and colloidal silica, the alkoxy group being converted to silanol by excess water. The coating film obtained by this coating material has superior weatherability and is excellent for substrate protection, however, it has poor toughness due to too high hardness (pencil hardness of not less than 9H), and when the thickness of the coating film is not less than 10 .mu.m, cracking easily will be formed if rapid change in temperature occurs in thermal-curing or use outdoors. Further, in coating process, the thickness of the coating film is often difficult to be regulated less than 10 .mu.m strictly, and especially around coated surface or coated substance or at concave part, the thickness of the coating film is liable to be over 10 .mu.m and inferior products are easily formed. Further, these coating materials require heat treatment at a high temperature of higher than about 100.degree. C. or long time heat treatment to obtain desired coating property, therefore, when coating is applied to a substrate having shape which uniform heating is difficult, a substrate having large scale or a substrate inferior in heat resistance, or when heating is difficult such as coating work outdoors, the coating materials can not be used and the use thereof is restricted. Regarding a coating material having a composition obtained by removal of the colloidal silica from the above-mentioned coating material, there are problems such as lacking in film-shaping property in coating and lowered strength of the coating film.
Further, these compositions for coating have problems that the silanol obtained by hydrolysis of the alkoxysilane has high reactivity, is gradually subjected to condensation reaction even at ambient temperature, easily become gel and inferior in stability. Especially when a paint is going to be prepared by using said composition for coating as a vehicle and adding a pigment, the stability further deteriorates and it becomes impossible to prepare a paint.
Japanese Patent Kokai Publication 168/1989 proposes a coating material in which immediately before coating a catalyst and water are added as a curing agent to a partial hydrolytic polycondensate of an alkoxysilane to convert the alkoxy group to a silanol hydroxy group. However, even this coating material has poor toughness, and cracking is easily formed in a coating film having a thickness of not less than 10 .mu.m. This coating material has excellent storability and a paint prepared from the coating material and a pigment added is relatively stable, however this coating material requires heat treatment at a high temperature of higher than about 100.degree. C. or long time heat treatment to obtain desired coating property, therefore, when coating is applied to a substrate having shape which uniform heating is difficult, a substrate having large scale or a substrate inferior in heat resistance, or when heating is difficult such as coating work outdoors, the coating material can not be used and the use thereof is restricted.
For the purpose of solving such defects, Japanese Patent Kokai Publication 268772/1988 proposes a coating material comprising a prepolymer mainly composed of a silicon alkoxide, a curing catalyst and water and curable around ambient temperature, however toughness has not improved, and process after coating of a precoat-metal, process after coating treatment of a polycarbonate plate and the like are impossible. Further, there are defects that coating property and curing property are poor and the curing property of the coating material is apt to be influenced by humidity.
Further, Japanese Patent Kokai Publication 175388/1992 discloses a coating material comprising a partial hydrolyzed oligomer of an organosilane, a silanol group-containing polyorganosiloxane and a curing catalyst. This coating material has advantages that the coating property and curing property are improved, curing at room temperature is possible, and it is not influenced by humidity, however the toughness of the coating material is not sufficiently improved.
Taken together, the above facts demonstrate that a coating material comprising as a main component an organoalkoxysilane or a hydrolyzate of an organoalkoxysilane provides a coating film which has high hardness, is difficult to be scratched and has excellent weatherability. However, this coating film is poor in stiffness and therefore cracking is apt to be formed in coating process or in use, and this phenomenon is remarkable when the thickness of the film is not less than 10 .mu.m. Further, this coating material requires baking at a high temperature of not lower than 100.degree. C., and though coating in a factory is possible, coating outdoors and at construction site is difficult. And it is demerit that the coating liquid has high reactivity and poor in storability.
Further, since the above-mentioned coating material is an inorganic coating material, the coating film thereof is liable to be inferior in adhesion to an organic substrate and an organic coating substrate.
There is also reported a resin carrying a hydrolyzable silane functional group and having as a main chain an organic resin such as acryl, polyester, epoxy, polyether, vinyl and the like (see Japanese Patent Kokai Publication 287206/1993, 302007/1993 and the like). However, these resins are inferior in weatherability and hardness of the coating film as compared with an inorganic resin containing as a main component an organoalkoxysilane, since the main chain thereof is composed of an organic resin. Further, also, Japanese Patent Kokai Publication 72928/1993 and 178998/1993 propose a reactive resin having a polymerizable acrylic functional group as a terminal or side chain and having a linear polysiloxane as a main chain. However, since the main chain is composed of a linear polysiloxane, excellent hardness of the resulting coating film is not obtained, and in some cases, this polysiloxane resin is a rubber elastomer and is not suitable as a resin for coating.
The above-mentioned inorganic cured body such as a concrete, slate, cement and the like is a material excellent in heat resistance and endurance, however the inorganic cured body has disadvantages that if the surface thereof is not coated, the surface is impregnated with water, is easy to be fouled and is inferior in acid resistance. Further, the appearance of the non-coated body is not anesthetic.
To supplement these defects, the surface of the inorganic substrate has been coated with an organic paint. However, the coating film formed by an organic paint has disadvantages that 1) it is poor in weatherability, 2) it is easily scratched due to low hardness, 3) it is inferior in adhesion to an inorganic substrate, and the like.
Then, there has been tried the application of an inorganic coating material such as water glasses and the like in place of the organic material, however, a satisfactory coating material has not been obtained in that efluorescence generates and it is porous.